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| United States Patent |
6,171,500
|
|
Ward
, et al.
|
January 9, 2001
|
Biological process for breaking oil-water emulsions
Abstract
A process for breaking an oil-water emulsion. The process comprises
contacting the oil-water emulsion with a bacterial culture produced by
growth in a liquid medium containing hydrocarbons under non-sterile
conditions. The oil-water emulsion and bacterial culture are contacted
under conditions that minimise degradation of the oil. The oil-water
emulsion is permitted to form an oil layer and a water layer, which are
then separated. The process is particularly useful in the treatment of
slop-oil emulsion in the petroleum industry.
| Inventors:
|
Ward; Owen P. (Waterloo, CA);
Singh; Ajay (Waterloo, CA)
|
| Assignee:
|
Petrozyme Technologies Inc. (Guelph, CA)
|
| Appl. No.:
|
294493 |
| Filed:
|
April 20, 1999 |
Foreign Application Priority Data
| Current U.S. Class: |
210/610; 210/800; 435/281 |
| Intern'l Class: |
C02F 003/00 |
| Field of Search: |
210/610,800,708
435/281
516/145,170
|
References Cited
U.S. Patent Documents
| 1753641 | Apr., 1930 | Beckman.
| |
| 3856667 | Dec., 1974 | Azarowicz.
| |
| 4349633 | Sep., 1982 | Worne et al.
| |
| 4392892 | Jul., 1983 | Wagner et al. | 134/25.
|
| 4432887 | Feb., 1984 | Zajic et al.
| |
| 5358760 | Oct., 1994 | Monticello et al.
| |
| 5411665 | May., 1995 | Scraggs et al.
| |
| 5551987 | Sep., 1996 | D'Addario et al. | 134/10.
|
| 5989892 | Nov., 1999 | Nishimaki et al.
| |
Other References
F.S. Manning, et al., "Oilfield Processing Volume Two: Crude Oil", PennWell
Publishing Co., Oklahoma, 1995, pp. 41, 42 and 44.
Petroleum Extension Service, "Treating Oilfield Emulsions", Fourth Edition,
The University of Texas at Austin, 1990, pp. 8 and 9.
Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Edition, Volume
Nine, "Elastomers, Polyisoprene to Expert Systems", Wiley-Interscience
Publication, John Wiley & Sons, New York, 1991, p. 409.
|
Primary Examiner: Simmons; David A.
Assistant Examiner: Prince; Fred
Attorney, Agent or Firm: Libert & Associates
Claims
What is claimed is:
1. A process for breaking an oil-water emulsion containing solids,
comprising:
a) contacting the oil-water emulsion with a bacterial culture produced by
growth in a liquid medium containing hydrocarbons under non-sterile
conditions, said oil-water emulsion and bacterial culture being contacted
under conditions that minimise degradation of said oil;
b) permitting the oil-water emulsion to form an oil layer and a water
layer, the solids present in the emulsion being permitted to settle to the
bottom of the water layer; and
c) separating each of the oil layer and the water layer so formed.
2. The process of claim 1 in which the culture consists of a mixed culture
previously grown on a petroleum or other oil-containing substrate.
3. The process of claim 1 in which the culture has a starting cell count in
the emulsion treatment system of 5.times.10.sup.6 -5.times.10.sup.9
Cfu/ml.
4. The process of claim 3 in which the culture has a starting call count in
the emulsion treatment system of greater than 5.times.10.sup.7 Cfu/ml.
5. The process of claim 1 in which a light petroleum, or vegetable oil or
other chemical or nutrient supplement or supplements is added to the
emulsion, with the bacterial culture, to promote breaking of the emulsion.
6. The process of claim 1 in which the culture consists of more than one
pure culture or a combination of one or more pure cultures with a mixed
culture.
7. The process of claim 1 in which molecules produced by the culture, or
fractions of cells which break or contribute to de-emulsification, are
added alone, or in combination with a culture, and/or oil or chemical
supplement.
8. The process of claim 1 in which the biological process is used
concurrently or sequentially in any order with another physical or
chemical treatment to break the emulsion.
9. The process of claim 1 in which the culture is generated by adding
nutrients to the emulsion, to promote selective growth of bacteria in the
emulsion.
10. The process of claim 9 in which a combination of added culture and
bacteria already present in the emulsion cause the emulsion to break.
11. The process of claim 1 in which partial breaking of the emulsion
occurs.
12. The process of claim 1 in which molecules of fractions of cells of the
culture are obtained as a crude aqueous extract or slurry of the culture.
13. The process of claim 1 in which the emulsion is a slop oil emulsion.
Description
The present invention is directed to a process for the breaking of an
oil-water emulsion, by contacting the emulsion with a bacterial culture
grown from hydrocarbons under non-sterile conditions, permitting oil and
water layers to separate and then separating each of the layers. The
oil-water emulsion may be an oil-in-water emulsion or a water-in-oil
emulsion.
An emulsion is usually a mixture of minute globules of one liquid dispersed
in a second non-miscible liquid. In the case of oil-water emulsions, the
emulsion may be in the form of oil globules in a continuous water phase
(oil-in-water) or, conversely, water globules in a continuous oil phase
(water-in-oil). Two immiscible liquids will tend to form an emulsion as
result of some type of physical or mechanical agitation of the two liquids
if an emulsifying agent, which promotes emulsion formation, is present.
Emulsifying agents found in water-petroleum oil emulsions include the
asphaltene and resin components of the oil, oil-soluble organic acids or
other chemicals originally present in the oil or which have been added to
it.
In oil exploration and production, there is substantial need for processes
to break crude oil:water emulsions with maximum oil recovery. As oil comes
from the oil well, some water i.e. so-called produced water, from the
formation is also recovered and the combined mixture of oil and water is
pumped into a field tank. The oil and water phases tend to separate, with
the oil phase rising to the top and the water phase being at the bottom.
An oil and water emulsion usually forms at the interface between the
phases.
Many such oil-water emulsions contain solids material. The solids may act
as a mechanical barrier, and prevent coalescence of emulsion droplets. In
the case of petroleum oil-water emulsions, the solids may consist of fine
particles also known as clay fines.
The emulsion cannot be transferred to the pipeline. Typically, pipeline
quality oil should contain less that one percent water and solids.
Therefore, the emulsions are usually brought to a treater facility which
aims to separate the emulsion into pipeline quality oil, which can be
sold, and water and solids. Treater facilities aim to neutralize the
properties of emulsifying agents or destroy them, thereby breaking the
emulsion.
A combination of physical and chemical treatments may be used to break the
emulsions e.g. centrifugation, heat, electrical treatment or use of
chemicals. Chemicals used in the breaking of emulsions include soap, fatty
acids and long chain alcohols. Chemical emulsion breakers when, for
example added to a water-in-oil emulsion, make the droplets of water merge
or coalesce. Larger droplets of water tend to settle out of oil faster
than smaller droplets.
The emulsion may also be broken electrically or mechanically. Heat
decreases emulsion viscosity, and increases the momentum of water and oil
molecules increase in the mobility of the emulsion droplets causes the
droplets to collide with each other more frequently which promotes
rupturing of the emulsion, coalescence of the droplets and separation of
the water and oil phases. The molecules of surfactant materials at the
interfaces in an emulsion are arranged with polar ends facing the water
phase and non-polar ends facing the oil phase. Electrical currents can
cause these molecules to rearrange, thereby disrupting the emulsion.
Emulsion treaters used in commercial processing of crude oils are typically
heat treaters or electrostatic treaters. However, even in these treaters a
difficult-to-break emulsion layer, often referred to as slop oil emulsion,
develops and accumulates in the treater and reduces treater capacity. One
of the problems associated with use of heat and chemical-based methods to
break emulsions is that the resulting slop oil emulsion tends to be more
stable and more difficult to break. The stabilizing agent of slop oil
emulsions is often a surface active material dissolved in one of the
phases. Thus, degrading or modifying the stabilizing agent represents a
key objective in attempting to break these emulsions. The volumes of slop
oil emulsions may amount to one percent of oil produced.
Residual emulsion material, slop oil emulsions, is a waste material which
either requires disposal or is accumulated on site. In some countries,
emulsions which survive chemical, thermal or other treatment in the
treater are dumped in oil pits or tanks or are transported in tankers to
lagoons. Alternatively, these emulsions are disposed of by pumping into
salt caverns or are sent to landfills.
Slop oil emulsions vary in their properties depending on the properties and
viscosity of the oil, the geologic formation where the oil originated, the
amount of water and solids, the salt content of the water, the nature of
the solids material, and the chemical or physical treater process.
Bacteria have a variety of properties which give them potential for use in
oil-water emulsion breaking processes. Bacteria can act in a number of
ways to modify the forces stabilizing an emulsion. For instance, bacterial
cells or their products may exhibit surfactant activity, may biotransform
surface active agents into agents which have less surfactant activity, may
degrade or transform oil components which are involved in emulsion
formation or may modify the pH at the emulsion interface. These or other
biological mechanisms may contribute to breaking an emulsion.
It is known to use single, pure bacterial cultures in the treatment of
emulsions. For instance, (a) Mycobacterium cuneatum, Mycobacterium
petroleophilum and some Psuedomonads cause coalescence of kerosene in
water emulsions containing a surfactant; (b) Nocardia amarae, grown in a
medium contained hexadecane, can de-emulsify oil-in-water emulsions that
were prepared by mixing kerosene or various pure alkanes with a
water-containing a surfactant; (c) acetoin, produced by Bacillus subtilis,
promotes de-emulsification of a 1% oil in water emulsion containing
Tween-80.TM. surfactant, and (d) pure cultures of Nocardia amarae,
Corynebacterium petrophilium and Torulopsis bombicola de-emulsify
oil-in-water and water-in-oil petroleum field emulsions. However, use of
single pure bacterial cultures is a disadvantage from a commercial
perspective, since preparation of the cultures requires use of sterilized
fermenter and culture media which have high associated capital and
operating costs.
U.S. Pat. No. 4,392,892 describes a process for separating hydrocarbons
from particulate solids using a crude extract of microbially-produced
glycolipids. U.S. Pat. No. 5,551,987 describes a process for treating of
solid waste or mud contaminated with hydrocarbons which involves
extracting the material with non-volatile organic solvent and contacting
the oily extract with microbes which produce biosurfactants.
PCT/CA98/00108 filed Mar. 20, 1998 describes a mixed biological process for
degradation of oil sludges, including refinery sludges, tank-bottoms, slop
oil or treater emulsions and others. The method involves forming an
oil-in-water emulsion in a reactor such that the reactor contains up to
50% by volume of hydrocarbons and where the hydrocarbon content in the
reactor is reduced by at least 25%.
An improved process for the breaking of oil-water emulsions that may be
operated In the field would be useful.
A biological process for the breaking or oil-water emulsions that may be
used in the field has now been found.
Accordingly, one aspect of the present invention provides a process for
breaking an oil-water emulsion comprising:
a) contacting the oil-water emulsion with a bacterial culture produced by
growth in a liquid medium containing hydrocarbons under non-sterile
conditions, said oil-water emulsion and bacterial culture being contacted
under conditions that minimise degradation of said oil;
b) permitting the oil-water emulsion to form an oil layer and a water
layer; and
c) separating each of the oil layer and the water layer so formed.
In a preferred embodiment of the process of the invention, solids are
present in the emulsion and such solids are permitted to settle to the
bottom of the water phase during step (b).
In a further embodiment, the culture consists of a mixed culture previously
grown on a petroleum or other oil-containing substrate, especially such a
culture having a starting cell count in the emulsion treatment system of
5.times.10.sup.6 -5.times.10.sup.9 Cfu/ml and preferably greater than
5.times.10.sup.7 Cfu/ml.
In a still further embodiment, a light petroleum, or vegetable oil or other
chemical or nutrient supplement or supplements may be added to the
emulsion, with the bacterial culture, to promote breaking of the emulsion.
In another embodiment, the culture may consist of more than one pure
culture or a combination of one or more pure cultures with a mixed
culture.
In a still further embodiment, molecules produced by the culture, or
fractions of cells which break or contribute to de-emulsification, may be
added alone, or in combination with a culture, and/or oil or chemical
supplement.
The present invention utilizes a microbial culture capable of oil sludge
biodegradation for the purpose of breaking pre-existing oil-water
emulsions with minimal degradation of the associated hydrocarbon. The
starting material for the process is either an oil-in-water or
water-in-oil emulsion, where solids may or may not be also present at the
oil-water interface. The process is operated to minimise substantial
degradation of hydrocarbons i.e. to break the emulsion with minimal
degradation of oil. Thus, hydrocarbon degradation is preferably 0-25% or
more preferably 0-10% of the hydrocarbon in the emulsion. The process uses
an oil degrading culture which can be prepared as described below.
In the biological process that has now been found, the oil-water emulsion
breaks with efficient separation of the emulsion into a top (upper) oil
layer and bottom (lower) aqueous layer. Solids associated with the
emulsion tend to settle at the bottom of the aqueous layer.
The method involves contacting the emulsion with a specified volume of
whole bacterial culture/culture extract, or with cells or extract
recovered from the culture using known methods such as centrifugation,
incubating the bacterial cell culture and the emulsion for a specified
period of time e.g. up to 5 days with or without shaking or mixing and
with or without aeration. The temperature used in the process should be
0-50.degree. C., preferably 10-40.degree. C. and more preferably
21-37.degree. C. The emulsion separates, and usually may be observed
visually to separate into a clearly defined top oil layer and a bottom
water layer with solids dropping to the base of the reactor.
The bacterial culture used in this invention may be mixed bacterial culture
produced by growth in a liquid medium containing hydrocarbons under
non-sterile conditions. The inoculum used in this invention may also be a
combination of pure cultures, or a combination of one or more pure
cultures with a mixed culture.
In a preferred method of obtaining the culture, the bacterial culture used
in the method of the present invention is a natural-occurring bacterial
culture. Such a culture may be isolated from a hydrocarbon-contaminated
soil or from hydrocarbon-containing sludge or from other environments,
including soil or activated sludge, which may be rich in
hydrocarbon-degrading bacteria, and inoculated in a basal medium, as
described herein. The bacterial culture is selected by its ability to grow
on petroleum hydrocarbons as the predominant source of carbon in the basal
medium. Bacterial enrichment techniques for isolation of a bacterial
culture capable of growing on hydrocarbons are well understood in the art.
Typical techniques comprise adding a sample of soil, sludge or other
material containing a large population of bacteria to an aqueous medium
containing hydrocarbons as the only or predominant carbon source. Other
chemical components including an inorganic nitrogen source, phosphorous
and salts necessary to support bacterial growth are also added. Such a
medium can be used to preferentially promote multiplication of
hydrocarbon-degrading bacteria using standard aerobic microbial
cultivation methods, including incubation in aerated microbial culture
vessels. By transfer of a small amount of the resultant growth culture to
further samples of the same medium and repeating the process one or more
times, an efficient hydrocarbon degrading culture is selected. The culture
can be maintained or stored using methods well known in the art.
In order to prepare a high density culture, the maintained culture may be
inoculated into an aqueous medium consisting of the nutrients described
herein, supplemented with petroleum hydrocarbons and incubated in an
aerated reactor or fermenter or other culture vessel. The preferred
inoculum volume is 0.1-20% by volume of total culture volume, preferably
1-5% by volume. The preferred concentration of petroleum hydrocarbons used
in this inoculum development medium is 0.5-5%, and can be obtained from
various sources including petroleum sludges, crude oils or refined oils
such as diesel oil. A typical aeration rate of the inoculum reactor is
0.1-1.0 volumes of air per volume of medium per minute, with the culture
incubated in the temperature range 20-37.degree. C. for 1-7 days,
preferably at 27-33.degree. C., at a pH generally maintained in the range
6.5-8.0, preferably in the range 7-7.5. The resultant bacterial culture
maybe used to inoculate the reactor containing the sludge to be degraded,
at a rate of 0.1-20% of total sludge volume, preferably 1-10%. Where a
much larger volume of inoculum is required, the resultant inoculum may be
transferred as an inoculum to a larger culture vessel and the culture
development process repeated on the larger scale.
Nutrients for the bacterial culture may also be added. A wide variety of
nutrients for the bacterial culture may be used, as will be understood by
persons skilled in the art. Such nutrients will include nitrogen,
phosphorus and potassium compounds, and would normally also include a
variety of other ingredients. In particular, the nutrients comprise
bioavailable nitrogen and phosphorus compounds. In embodiments, the amount
of nitrogen is in the range of 50-1000 ppm and preferably 400-700 ppm, and
the amount of phosphate is in the range of 10-200 ppm and preferably
50-150 ppm. In addition to nitrogen and phosphorus compounds, the nutrient
may also contain optimized concentrations of compounds other than
nitrogen, phosphorus, carbon, oxygen and sodium, required to support
bacterial growth and therefore it is normally necessary to add to the
reactor one or more of magnesium, manganese, inorganic or organic sulphur,
calcium, iron, copper, cobalt, zinc, boron and molybdenum. It will be
appreciated that a guide for selection of the relative amounts of
nitrogen, phosphorus and other required nutrients is to relate their
concentrations to the amounts of these components present in bacterial
cells.
By providing an appropriate balance of nutrients and by adjustment of
nutrient concentration, it is possible to achieve high levels of growth of
hydrocarbon degrading bacteria and thus accelerated rates of hydrocarbon
degradation. For example, Greasham (1993) "Biotechnology, a multivolume
comprehensive treatise" (Eds, Rehm, H. J., et al) Vol. 3, p.131, VCH,
Weinheim) has reported the typical non-carbon elemental composition of
major bacterial components to be nitrogen 12.5%; phosphorus, 2.5%;
potassium, 2.5%; sodium, 0.8%; sulphur, 0.6%; calcium, 0.6%; magnesium,
0.3%; copper, 0.02%; manganese, 0.01% and iron, 0.01%. Use of appropriate
concentrations and ratios of nutrients tends to avoid a situation where
growth is limited by depletion of one essential nutrient while all other
nutrients may be present in excess.
Techniques for the preparation of the bacteria will be understood by
persons skilled in the art.
The culture used is characterized by its capacity to degrade one or more
components of oil, or of chemical or nutrients added to oil, or to
transform oil components and/or added chemical or nutrients to other
products in a manner which breaks the emulsion. In addition, the microbial
cells themselves or intracellular or extra-cellular products from the
cells produced before or after contacting the culture with the oil-water
emulsion may contribute to breaking the emulsion. Cultures having any
combination of the above properties and which contribute to breaking the
emulsion under the proper mechanical mixing and/or aeration conditions are
within the scope of the invention. The invention also covers use of
molecules produced by the cultures and fractions of cells which result in
the breaking of the emulsion. In a preferred embodiment of the method of
the invention, the culture consists of a mixed culture previously grown on
a petroleum or other oil-containing substrate and having a starting call
count in the emulsion treatment system of 5.times.10.sup.6
-5.times.10.sup.9 Cfu/ml and preferably greater than 5.times.10.sup.7
Cfu/ml. Such a culture is added to the water-oil emulsion and mixed by
stirring and/or aeration for a period of time to break the emulsion.
During the reaction, one or more components of the emulsion are
biotransformed or biodegraded, or otherwise transformed to disrupt the
emulsion.
A light petroleum, or vegetable oil or other chemical or nutrient
supplement or supplements may be added to the emulsion with the bacterial
culture to promote breaking of the emulsion.
As noted above, the culture may consist of more than one pure culture or a
combination of one or more pure cultures with a mixed culture. Preferably,
the molecules or fractions are prepared as a crude aqueous extract or
slurry of the culture.
In a further embodiment, molecules produced by the culture, or fractions of
cells which break or contribute to de-emulsification, may be added alone
or in combination with a culture, and/or oil or chemical supplement.
In a preferred embodiment, the cells, or molecules produced by the cells or
fractions of cells are prepared in an aerated aqueous medium containing a
hydrocarbon oil and/or vegetable oil substrate, under aseptic or non
aseptic conditions. The bacteria are added at a concentration designed to
break the emulsion within a given time period. It is understood that in
general the higher the concentration of the culture, the faster the
de-emulsification process.
In yet a further embodiment, the emulsion may be broken by using a
combination of this biological method and other chemical or physical
treatments, such as are described above. In a further embodiment,
nutrients are added to the emulsion which promote selective growth of
bacteria already present in the emulsion which have a capacity to break
the emulsion.
The process may be operated to fully break the emulsion or partially break
the emulsion. In the latter, remaining emulsion could be subjected to
similar or other procedures to break the emulsion in subsequent steps.
The method of the present invention may be used in the treatment of
water-oil emulsions, especially water-oil emulsions in the petroleum
industry e.g. slop oil emulsion, to effect separation of an oil phase. The
method is operated to minimize oil degradation, as oil is the prime
commercial product of the method.
The present invention is illustrated by the following examples.
In the examples, unless noted otherwise, petroleum hydrocarbon degrading
bacteria were selected by their ability to grow on petroleum hydrocarbons
as the sole carbon source. An actively growing population of mixed culture
was maintained (10.sup.9 to 10.sup.10 CFU/ml) in cyclone fermentors by
feeding either diesel, motor oil, refinery oil sludge or heavier
hydrocarbon fraction of oily sludge. The general methods and nutrients
used for growth of the culture are as described in our earlier patent
application, PCT/CA98/00108.
In biological treatment tests, a concentrated inoculum was prepared by
centrifuging the culture at 5000 rpm for 20 min and resuspending the cells
in a small amount of water. The treatment flasks received bacterial
culture to the final inoculum concentration of 5 to 50% (5.times.10.sup.7
to 5.times.10.sup.8 CFU/ml). The flasks were incubated on a rotary shaker
(200 rpm) at 30.degree. C. for 48-72 hr. The flasks were let stand for 1
hr for the separation of oil from water and solids. The oil was analyzed
for the contents of water, solids and total hydrocarbons (dichloromethane
(DCM) extractables).
EXAMPLE I
Various emulsion samples were obtained from different sources. The samples
were analyzed for water and solids content, and total hydrocarbons as DCM
(dichloromethane) extractables. The characteristics (wt %) of different
emulsion samples are shown in Table 1.
TABLE 1
Interface
treater Slop oil emulsions
emulsion A B C D
Components (wt %)
DCM extractables 19.2 72.5 53.9 61.0 79.5
Hexane extractables 15.2 56.3 46.4 47.1 65.4
Solids 4.5 9.8 3.2 5.0 2.0
Water 76.3 17.7 42.8 34.0 18.5
Hydrocarbon fractions (% of total)
Saturates 19.8 21.9 21.7 12.9 --
Aromatics 50.0 47.8 54.7 37.2 --
Resins 9.4 8.0 9.6 5.3 --
Asphaltenes 20.8 22.3 14.0 22.8 17.7
Interface treater emulsion i.e. an emulsion from the interface of a
treater, and slop oil emulsions have been described previously. Total
hydrocarbons and water in these varied from 19 to 80% and from 17 to 76%,
respectively. Analysis indicated a similar hydrocarbon composition in all
of these samples.
EXAMPLE II
In a preliminary experiment, 47 g of the Interface emulsion sample were
taken in 250 ml Erlenmeyer flasks. The flasks were supplemented with the
nutrient medium and mixed culture. The nutrient medium consisted of (per
liter): KH.sub.2 PO.sub.4, 10.0 g; Na.sub.2 HPO.sub.4, 15.0 g;
MgSO.sub.4.7 H.sub.2 O, 2 g; Na.sub.2 CO.sub.3, 1.0 g; CaCl.sub.2.2
H.sub.2 O, 0.5 g; FeSO.sub.4, 0.05 g; urea, 20 g; yeast extract, 10 g, and
trace metal solution, 30 ml. The trace metal solution contained (per
liter): ZnCl.sub.2.4 H.sub.2 O, 0.0144 g; CoCl.sub.2.6 H.sub.2 O, 0.012 g;
Na.sub.2 MoO.sub.4.2 H.sub.2 O, 0.012 g; CuSO.sub.4.5 H.sub.2 O, 1.9 g;
H.sub.3 BO.sub.4, 0.05 g; and HCl, 35 ml. The initial pH of the nutrient
media was adjusted to 7.0. The flasks were incubated on a rotary shaker
(200 rpm) at 30.degree. C. for 48 hr. The flasks were let stand for 1 hr
for the separation oil from water and solids. The bacterial cell count of
the culture in the final reaction mixture was 5.times.10.sup.8 CFU/ml.
The visual observations in these flasks are shown in Table 2.
TABLE 2
Emulsion Water Medium Culture
(g) (ml) (ml) (ml) Observations
47 4 0 0 Emulsion remains
as such
47 1 3 0 Partial oil
separation with
cloudy water
47 0 3 1 Oils separation,
clear water,
solids at bottom
47 0 3 1 Oils separation,
clear water,
solids at bottom
47 0 3 0.4 Oils separation,
clear water,
solids at bottom
47 0 3 0.2 Oils separation,
clear water,
solids at bottom
47 0 3 0.1 Partial oil
separation with
clear water
A nearly perfect separation was observed in the flasks containing only
culture or nutrients and culture, oil layer on the top, a clear water
phase in the middle and the solids/cells fell to the bottom. A cell
concentration of 10-50% (1-5.times.10.sup.8 CFU/ml in the oil water
emulsion) was effective in breaking the emulsion.
EXAMPLE III
In this example, slop oil emulsion from different sources were treated with
the culture used in Example I. The flasks were incubated on a rotary
shaker (200 rpm) at 30.degree. C. for 72 hr. The flasks were let stand for
1 hr. for the separation of oil from water and solids. Recovered oil was
analyzed for residual water, total hydrocarbons, and solids. The bacterial
cell count of the culture in the final reaction mixture was about
1.times.10.sup.8 CFU/ml. The initial water contents in Slop oil A, B and C
were 17.7, 42.8 and 34.0% respectively.
Results are shown in Table 3.
TABLE 3
Emulsion Characteristics
type and of recovered oil
amount Water Medium Culture Water Solids DCM
(g) (ml) (ml) (ml) (%) (%) extractables
Slop A, 5 0 0 11 3 86
45 g 5 0 1 1 2 97
0 5 1 1 2 97
Slop B, 5 0 0 24 5 71
50 g 5 0 1 5 3 92
0 5 1 8 2 90
Slop C, 5 0 0 8 2 90
45 g 5 0 1 0.2 1 98.8
0 5 1 0.2 1 98.8
5 0 2 0.1 1 98.9
The results indicate that the emulsion was successfully broken in all the
slop oil samples tested, with 88-99% reduction of water content in
recovered oil. Water content in recovered oil was <1% in slop oil A and C,
and <5% in slop oil B. No significant effect of addition of media
nutrients was observed.
EXAMPLE IV
Slop oil A was treated in 250 ml shaker flasks with the culture used in
Example I, sewage sludge and proteins. The flasks were incubated on a
rotary shaker (200 rpm) at 30.degree. C. for 72 h. The flasks were let
stand for 1 hr for the separation of oil form water and solids. Recovered
oil was analyzed for water, total hydrocarbons, and solids. The bacterial
cell count of the culture in the final reaction mixture was about
1.times.10.sup.8 CFU/ml. The initial water content in Slop oil A was
17.7%.
Results are shown in Table 4.
TABLE 4
Characteristics
of recovered oil
Slop Med- Sol- DCM
oil Water ium Culture/Other Water ids extractables
(g) (ml) (ml) additives (%) (%) (%)
50 50 0 None 20 3 77
50 50 0 1 ml culture 4 3 93
50 40 10 1 ml culture 1 3 96
25 65 10 1 ml culture 1 2 97
50 40 0 10 ml 20 2 78
sewage sludge
50 50 0 0.1 g extract 10 1 89
50 50 0 0.01 g 15 3 82
bovine albumen
Maximum removal of water was achieved when the emulsion was inoculated with
the mixed culture. Addition of sewage sludge, yeast extract or bovine
albumen protein did not effect the emulsion breaking.
EXAMPLE V
In this example, Slop oil B was treated with mixed culture, sewage sludge
or proteins in shaker flasks for 3 days at 30.degree. C. on a rotary
shaker (200 rpm). The flasks were let stand for 1 hr for the separation of
oil from water and solids. Recovered oil was characterized. The bacterial
cell count of the culture in the final reaction mixture was about
1.times.10.sup.8 CFU/ml. Initial water content in slop oil B was 42.8%.
The results are shown in Table 5.
TABLE 5
Characteristics
of recovered oil
Slop Med- Sol- DCM
oil Water ium Culture/Other Water ids extractables
(g) (ml) (ml) additives (%) (%) (%)
50 50 0 None 35 2 63
80 10 10 1 ml culture 5 3 92
90 0 10 1 ml culture 8 3 89
50 50 0 0.1 g 29 2 69
yeast extract
50 50 0 0.01 g 23 2 75
bovine albumen
50 40 0 10 ml 35 2 63
sewage sludge
Maximum removal of water from slop oil B was achieved when the emulsion was
inoculated with the mixed culture in the presence of nutrient medium.
Addition of sewage sludge, yeast extract or bovine albumen protein did not
significantly affect the emulsion breaking.
EXAMPLE VI
In this example, the effect of water content on recovery of oil from Slop
oil A and B was investigated. Slop oils was treated with the same mixed
culture for 3 days at 30.degree. C. on a rotary shaker (200 rpm). The
flasks were let stand for 1 hr for the separation of oil from water and
solids. Each flask received 1 ml of mixed culture. The bacterial cell
count of the culture in the final reaction mixture was about
1.times.10.sup.8 CFU/ml. Initial water contents in slop oil A and B were
17.7& and 42.8%, respectively. The recovered oil was characterized.
The results are shown in Table 6.
TABLE 6
Water Slop oil A Slop oil B
Slop addition Water Solids DCM Water Solids DCM
oil (g) (ml) (%) (%) extractables (%) (%) extractables
100 0 1 2 97 10 3 87
90 10 2 2 96 5 3 92
80 20 1 2 97 27 2 71
70 30 16 2 82 26 2 72
60 40 18 2 82 27 2 71
50 50 -- -- -- 27 2 71
Effective emulsion breaking and maximum reduction of water in oil emulsions
was observed when water addition was less that 20% in slop oil A and less
than 10% in slop oil B.
EXAMPLE VII
In this example, effect of biological treatment on the breaking of emulsion
and biodegradation of total hydrocarbons and hydrocarbon fractions of the
slop oil was investigated. Slop oil C. was treated with the mixed culture
for 2 days at 30.degree. C. on a rotary shaker (200 rpm). The whole flask
was extracted with dichloromethane and different hydrocarbon fractions
were analyzed.
The results are shown in Table 7.
TABLE 7
Hydrocarbons % Degradation
DCM extractables 8.2
Hexane extractables 14.8
Saturates 11.6
Aromatics 4.8
Resins 13.2
Asphaltenes 0
Results indicate degradation of all the hydrocarbon fractions except
asphaltene.
EXAMPLE VIII
In this example, effect of shaking on breaking of emulsion and oil recovery
was investigated in 250 ml shake flasks. To 50 g Slop oil B, 5 ml nutrient
medium and 5 ml mixed culture inoculum (1.times.10.sup.8 CFU/ml) was
added. The flasks were vortexed for 1 min to distribute the inoculum in
emulsion. One set of flasks was incubated at 30.degree. C. under
stationary condition and another set of flasks were incubated at
30.degree. C. on a rotary shaker at 200 rpm. The bacterial cell count of
the culture in the final reaction mixture was about 1.times.10.sup.8
CFU/ml. Initial water content in slop oil B was 42.8%.
Recovered oil was characterized and the results are shown in Table 8.
TABLE 8
Characteristics of recovered oil
Culture Time Water Solids DCM
condition (d) (%) (%) extractables
Stationary 3 20 3 77
7 5 3 92
14 4 3 93
Shaken 3 8 2 90
7 1 2 97
Biological treatment under both stationary and shaken culture conditions
resulted in emulsion breaking. However, maximum removal of water from the
recovered oil was observed in shaken culture.
EXAMPLE IX
In this example, effect of different additives on breaking of emulsion and
oil recovery was investigated. Slop oil B was treated with the mixed
culture in the presence of different additives viz peanut oil, diesel and
gasoline, for 3 days at 30.degree. C. on a rotary shaker (200 rpm). The
flasks were let stand for 1 hr for the separation of oil from water and
solids. The bacterial cell count of the culture in the final reaction
mixture was about 1.times.10.sup.8 CFU/ml in each flask. Initial water
content in slop oil B was 42.8%.
Recovered oil was characterized and the results are shown in Table 9.
TABLE 9
Characteristics of recovered oil
Concentration Water Solids DCM
Additives (%) (%) (%) extractables
None -- 10 3 87
Peanut Oil 0.1 1 2 97
Diesel 0.1 3 1 96
0.5 1.5 3 95.5
1.0 1 3 96
2.0 0.05 3 96.9
4.0 0.1 2 97.9
Results indicate that addition of vegetable oil or petroleum products was
beneficial in emulsion breaking and removal of water. Increase in diesel
concentration increased the removal of water from the emulsion.
EXAMPLE X
In this example, biological treatment of slop oil emulsion was scaled up in
a stirred reactor. About 1.5L of slop oil D was mixed with 150 ml of the
culture (.about.1.times.10.sup.8 CFU/ml), 15 ml diesel and 15 ml nutrient
medium in a 2L beaker. Contents were incubated at room temperature with
continuous stirring using a laboratory stirrer equipped with a ring guard
3 blade propeller (dia. 4 cm) at about 250 rpm. At different time
intervals, 50 ml samples were taken out in a 100 ml beaker and let stand
for 2 hr for the separation of oil from water and solids. The bacterial
cell count of the culture in the final reaction mixture was about
1.times.10.sup.8 CFU/ml.
The results are shown in Table 10.
TABLE 10
Characteristics of recovered oil
Incubation Water Solids DCM
Time (h) (%) (%) extractables
0 18.5 2.0 79.5
24 8.0 -- --
48 7.0 -- --
72 0.5 1.0 98.5
96 0.5 0.7 98.8
In the stirred reactor, water and solid contents reduced within 3 days to
0.5% and 1.0%, respectively.
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